Field of the Invention
The present invention relates to an optical element, a light source device using the optical element, and a projection display apparatus.
Description of the Related Art
In recent years, a projector including a light source device including a solid light source, such as a laser diode (hereinafter referred to as LD) light source and an LED light source, and a fluorescent element that converts a portion of excitation light emitted from the solid light source into fluorescent light having a wavelength different from the wavelength of the excitation light has been developed.
Such a light source device is disclosed in JP 2012-189938 A.
JP 2012-189938 A discloses a light source device including a light source unit that includes a plurality of blue LDs, a light source unit including a plurality of red LDs, and a fluorescent element having a fluorescent light layer that is provided on a transmissive substrate and emits green-color light by excitation by blue-color light. With a portion of the light from the blue LD working as excitation light and the rest of the portion of the light passing through the fluorescent element as unconverted light, the fluorescent element emits blue-color light, green-color light, and red-color light.
As in the light source device disclosed in JP 2012-189938 A, in which the fluorescent element having a fluorescent light layer that emits fluorescent light by excitation by blue-color light, the light amount of blue-color light tends to be smaller than the light amount of green-color light and red-color light, because the blue-color light is used as excitation light. Therefore, the color balance of a projected image might be degraded.